Method of managing conditioning fluid of a thermal management system for an aircraft

Abstract

The present invention relates to a method of managing conditioning fluid of a thermal management system (10) for an aircraft (100), comprising: obtaining an indication (36) that a conditioning fluid (20) present in at least one passage (12) for conditioning at least one aircraft component (14) has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning; removing, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to a reservoir (24) at least temporarily in fluid communication with said at least one passage, thereby at least partly emptying said at least one passage of conditioning fluid; causing the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and returning the conditioning fluid having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage.

Description

[0001] METHOD OF MANAGING CONDITIONING FLUID OF A THERMAL MANAGEMENT SYSTEM FOR AN AIRCRAFT

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a method of managing conditioning fluid of a thermal management system for an aircraft. The present disclosure also relates to a thermal management system, to an aircraft comprising such a thermal management system, and to a computer program product.

[0004] BACKGROUND

[0005] Aircrafts, in particular electric or hybrid electric aircrafts, may have a thermal management system for cooling aircraft components such as propulsion batteries e.g. using liquid coolant.

[0006] For example, US2021143492A1 FIG. 11 shows a stack of six battery modules in a circuit for a liquid coolant. The circuit has a header inlet which sends coolant to distribution ports of the modules, and a header outlet which receives coolant from collection ports of the modules. The circuit also has an electric pump for circulating the coolant around the circuit, and a heat exchanger based on a radiator and cooler fan to reduce the temperature of the pumped coolant and thereby remove waste heat from the modules. In addition, the circuit has a heater element which can heat the coolant in a plenum before entry into the header inlet, the heater and the heat exchanger being controllable such that the coolant is either cooled by the heat exchanger or heated by the heater. In this way, an option is available to warm the batteries. In particular, battery modules are typically positioned in an unheated region of the aircraft, and there may therefore be long periods of time where the batteries are exposed to very low ambient temperatures during flight when the batteries are not in use. The liquid coolant may be water or water-glycol (e.g. a 50:50 mixture).

[0007] Moreover, US2022281351A1 discloses a battery heating system which includes an internal combustion engine, wherein hot engine coolant flows through an engine coolant valve. The engine coolant valve may be operated by a control system to allow some, all, or none of the hot engine coolant to flow into a heat exchanger. Battery coolant passes through the heat exchanger where it may be selectively heated by transferring heat from the engine coolant. The battery coolant then enters a battery pack. Battery coolant exiting the battery pack passes through a battery coolant valve where the control system may selectively allow battery coolant to flow to either a battery cooling radiator or directly to a battery coolant reservoir. Battery cooling fluid from the battery coolant reservoir is then pumped through the heat exchanger to reenter the battery pack. The control system selectively operates the engine coolant valve to permit hot engine coolant to enter the heat exchanger when a battery temperature sensor indicates that the battery pack is below its minimum operating temperature. The control system also selectively operates the engine coolant valve to restrict hot engine coolant from entering the heat exchanger when battery temperature approaches the maximum operating temperature of the battery pack. In addition to sensor information from the hybrid powertrain system, additional information may in US2022281351A1 be considered when determining whether the battery pack(s) should be heated or cooled. For example, flight path information (e.g., including expected flight path altitudes), weather forecasts or actual sensed weather conditions (e.g., by other aircraft), and any other information may be used to determine whether the battery pack(s) should be heated or cooled.

[0008] US2023369680A1 discloses a battery assembly comprising a thermal regulation system which comprises a main circuit containing a heat-transfer composition and a secondary circuit containing an additional heat-transfer composition, the two circuits being thermally connected by at least one heat exchanger. When it is circulating, the heat-transfer composition in the main circuit can be set in motion by a first pump. The additional heattransfer composition in the secondary circuit is set in motion by a second pump. The secondary circuit comprises an expansion valve making it possible to ensure the evaporation of the additional heat-transfer composition in the heat exchanger, in order to cool the heat-transfer composition of the main circuit. At least one battery module is fluidically incorporated in the main circuit. In a circulating system, a tank can optionally be provided in the main circuit in order to receive an excess of heat-transfer composition in liquid form. In battery cooling mode, the first pump withdraws the heat-transfer composition from the tank and sends it to the battery module. The heat-transfer composition remains in the liquid state on passing through the battery module. The heattransfer composition subsequently passes through the heat exchanger. The additional heat-transfer composition is expanded in the expansion valve and then completely or partially vaporizes in the heat exchanger. The heat-transfer composition transfers heat to the additional heat-transfer composition. The heat-transfer composition subsequently returns to the tank. US2023369680A1 also discloses that a heat-transfer composition can be sprayed over the cells by monodirectional or multidirectional nozzles. The composition can be recovered in a tank and recirculated by a pump. A heat exchanger and / or a heating means (for example a resistance heating means) can be arranged in the reservoir, or upstream or downstream of the pump, to make it possible to supply or remove heat to or from the composition. In this variant, the liquid composition may be brought into contact with the surface of the cells only when there is a need to regulate the temperature of the battery. The rest of the time, and in particular when the battery is not in operation, the surface of the cells may not be in contact with the heat-transfer composition.

[0009] SUMMARY

[0010] In a thermal management system for conditioning aircraft components such as propulsion batteries e.g. using a conditioning fluid such as liquid coolant, if the aircraft is subjected to extreme temperatures (e.g. down to -10°C or below -30°C), for example when parked overnight during winter in say northern Sweden, the temperature of the liquid coolant in or near the aircraft components may reduce to an unacceptable level including freezing. Or the temperature of the liquid coolant could increase to an unacceptable level, for example when the aircraft is parked in extreme heat (e.g. above +40°C).

[0011] An object of the present disclosure is to provide a method of managing a conditioning fluid of a thermal management system of an aircraft which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies.

[0012] This object is obtained by a method of managing conditioning fluid of a thermal management system for an aircraft, wherein the method comprises: obtaining an indication that a conditioning fluid, which conditioning fluid is present in at least one passage of the thermal management system for conditioning (cooling or heating) at least one aircraft component associated with said at least one passage, has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning; removing, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to a reservoir at least temporarily in fluid communication with said at least one passage , thereby at least partly emptying said at least one passage of conditioning fluid; causing the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and returning conditioning fluid having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage.

[0013] The preset invention is at least partly based on the understanding that by removing conditioning fluid from the at least one passage in response to obtaining said indication, unnecessary operation of the thermal management system may be avoided, as absent obtaining said indication the conditioning fluid may just be kept in the at least one passage also at a time when the at least one aircraft component does not require cooling or heating. Moreover, no (more) antifreeze has to be added to the conditioning fluid to cope with really low temperatures e.g. while the aircraft is parked, which antifreeze could give the conditioning fluid other, unwanted properties.

[0014] Absent obtaining said indication, the conditioning fluid may be kept in the at least one passage at the time when the at least one aircraft component does not require conditioning. In this way, unnecessary operation of the thermal management system is avoided.

[0015] The at least one aircraft component may be located onboard the aircraft. The aircraft may be parked on ground at the time when the (onboard) at least one aircraft component does not require conditioning. Alternatively, the aircraft could be flying at the time when the (onboard) at least one aircraft component does not require conditioning. In another embodiment, the present method may be performed when the at least one aircraft component is not located on board an aircraft, for example in conjunction with shipping of the at least one aircraft component.

[0016] The at least some conditioning fluid may be removed from said at least one passage to the reservoir in response to obtaining said indication and before the conditioning fluid freezes. Once frozen, it would not be possible to e.g. pump the conditioning fluid from the at least one passage to the reservoir.

[0017] Causing the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range may include melting the conditioning fluid that has frozen in the reservoir. Once melted, the conditioning fluid may readily be e.g. pumped from the reservoir back to the at least one passage.

[0018] Conditioning fluid having its temperature within said predetermined operating temperature range may be returned from the reservoir to said at least one passage in time to meet a requirement to condition said at least one aircraft component.

[0019] Said indication may be based on at least one of: input from at least one temperature sensor of the thermal management system; a temperature forecast for the location of the aircraft at the time when the at least one aircraft component does not require conditioning; a (scheduled) time of departure for the aircraft’s next flight; and a time when the at least one aircraft component requires conditioning. The indication may for example be based on input from at least one temperature sensor of the thermal management system and a (scheduled) time of departure for the aircraft’s next flight. In another example, the indication may be based on a temperature forecast for the location of the aircraft at the time when the at least one aircraft component does not require conditioning and a (scheduled) time of departure for the aircraft’s next flight. In yet another example, the indication may be based a temperature forecast for the location of the aircraft at the time when the at least one aircraft component does not require conditioning and a time when the at least one aircraft component requires conditioning.

[0020] When to return the conditioning fluid in the reservoir to said at least one passage may be based on at least one of: a (scheduled) time of departure for the aircraft’s next flight, and an ambient temperature of the aircraft.

[0021] Said reservoir may be onboard the aircraft. Alternatively, said reservoir may be external of said aircraft. In the latter case, the reservoir may form part of a ground support equipment (GSE) connectable to the aircraft.

[0022] Said reservoir may be located further from the at least one aircraft component than said at least one passage. By removing conditioning fluid to a reservoir located further from the at least one aircraft component where its temperature is caused to be within the predetermined operating temperature range e.g. by heating, there is no accidental and / or uncontrolled heating of the at least one aircraft component when e.g. melting the conditioning fluid. The conditioning fluid may be removed from the at least one passage to the reservoir and returned from the reservoir to the at least one passage by at least one pump. The at least one pump may for example be on board the aircraft. The at least one pump may also be configured to circulate the conditioning fluid in a fluid circuit comprising said at least one passage when the at least one aircraft component requires conditioning.

[0023] The conditioning fluid removed to the reservoir may be trapped in the reservoir by closing at least one valve associated with the reservoir. In this way, it may be ensured that the conditioning fluid is just not circulated through the reservoir in case the reservoir is included in the aforementioned fluid circuit. Moreover, the conditioning fluid when about to return from the reservoir may be released from the reservoir by opening (the) at least one valve associated with the reservoir.

[0024] The method may further comprise determining, by at least one of a conditioning fluid flow meter and visual inspection, that at least a predetermined sufficient amount of the conditioning fluid is removed from the at least one passage.

[0025] The temperature of the conditioning fluid in said reservoir may be caused to be within said predetermined operating temperature range by a heating and / or cooling element associated with said reservoir.

[0026] At least one of the at least one pump and the heating and / or cooling element may be powered by a power source external of the aircraft. This may prevent unintentional activation of in particular the heating / cooling element on board the aircraft. Alternatively, at least one of the at least one pump and the heating and / or cooling element may be powered by a power source on board the aircraft, which (onboard) power source could be removed before flying.

[0027] Said indication may be obtained by at least one control unit.

[0028] Said at least one aircraft component may be at least one propulsion battery unit of said aircraft. Alternatively, the at least one aircraft component may for example be an electric motor configured to be used in propulsion of the aircraft, or any other component (on board the aircraft) containing a conditioning fluid that may freeze within the operational window of the aircraft (e.g. -55°C) or change its characteristics at high temperatures.

[0029] Said conditioning fluid may be a liquid coolant, such as ethylene glycol mixture. According to a second aspect of the present invention, there is provided a thermal management system for an aircraft, the thermal management system comprising: at least one passage for conditioning at least one aircraft component associated with said at least one passage; a reservoir at least temporarily in fluid communication with said at least one passage; and at least one control unit configured to: obtain an indication that a conditioning fluid present in the at least one passage has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning; control at least one pump to remove, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to the reservoir, thereby at least partly emptying said at least one passage of conditioning fluid; control a heating and / or cooling element associated with said reservoir to cause the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and control (the) at least one pump to return conditioning fluid having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage. This aspect may exhibit the same or similar features and / or technical effects as the first aspect, and vice versa.

[0030] According to a third aspect of the present invention, there is provided an aircraft, comprising: a thermal management system according to the second aspect; and the at least one aircraft component. The aircraft may for example be one or more of: an airplane, an electric propulsion aircraft, a hybrid electric propulsion aircraft, a fixed-wing aircraft, a conventional take-off and landing (CTOL) aircraft, a monoplane, and adapted to be flown by a pilot on board the aircraft. The aircraft may for example comprise one or more of: wings, braced wings, a fuselage, an empennage, a cockpit, a passenger cabin, flight control surfaces (such as ailerons, elevators, a rudder, flaps, air brakes, etc.), and (wheeled and / or retractable) landing gear.

[0031] According to a fourth aspect of the present invention, there is provided a computer program product comprising computer program code to perform, when executed on a computer, the steps of: obtaining an indication that a conditioning fluid present in at least one passage for conditioning at least one aircraft component associated with said at least one passage has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning; controlling at least one pump to remove, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to a reservoir at least temporarily in fluid communication with said at least one passage, thereby at least partly emptying said at least one passage of conditioning fluid; controlling a heating and / or cooling element associated with said reservoir to cause the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and controlling (the) at least one pump to return the conditioning fluid having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage. The computer may be (included in) the aforementioned at least one control unit. This aspect may have the same or similar features and / or technical effects as any one of the previous aspects, and vice versa.

[0032] According to a fifth aspect of the present invention, there is provided a computer- readable storage medium comprising the computer program product according to the fourth aspect. The computer-readable storage medium may be a non-transitory computer-readable storage medium.

[0033] According to a sixth aspect of the present invention, there is provided an electrical signal embodied on a carrier wave and propagated on an electrical medium, the electrical signal comprising the computer program product according to the fourth aspect.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

[0036] Fig. 1 is a flowchart of a method of managing conditioning fluid of a thermal management system.

[0037] Fig. 2 schematically illustrates one or more embodiments of a thermal management system.

[0038] Fig. 3 schematically illustrates another embodiment of a thermal management system. Figs. 4a-b is each a perspective view of an aircraft comprising a thermal management system.

[0039] DETAILED DESCRIPTION

[0040] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The method and / or system disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0041] The terminology used herein is for the purpose of describing particular aspects of the disclosure only, and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0042] Fig. 1 shows a method of managing conditioning fluid of a thermal management system 10 for an aircraft 100.

[0043] With further reference to fig. 2, the thermal management system 10 may comprise at least one passage 12 for conditioning at least one aircraft component 14 located on board the aircraft 100 and associated with the at least one passage 12. The at least one passage 12 may for example be provided in the at least one aircraft component 14. The least one passage 12 may be included in a fluid circuit 16 of the thermal management system 10.

[0044] The thermal management system 10 may further comprise at least one pump 18 arranged to circulate a conditioning fluid 20 inside the fluid circuit 16. Accordingly, the conditioning fluid 20 may circulate through the at least one aircraft component 14 inside the at least one passage 12 for conditioning (i.e. heating or cooling) the at least one aircraft component 14.

[0045] The at least one aircraft component 14 may for example be at least one propulsion battery unit of the aircraft 100. In case the at least one aircraft component 14 is a plurality of propulsion battery units, the propulsion battery units may for example be fluidly connected in parallel in the fluid circuit 16. The conditioning fluid 20 may be a coolant. The conditioning fluid 20 may be a liquid, at least in its predetermined operating temperature range. The conditioning fluid 20 may for example be ethylene glycol mixture. The predetermined operating temperature range (T1-T2) could for example be -30°C to +100°C.

[0046] The thermal management system 10 may further comprise a heat exchanger 22. The heat exchanger 22 may be configured to cool the conditioning fluid 20 in the fluid circuit 16. The heat exchanger 22 may for example be a (ram) air-cooled heat exchanger.

[0047] The thermal management system 10 may further comprise a reservoir 24. The reservoir 24 could also be (referred to as) a tank. In fig. 2, the reservoir is on board the aircraft 100. The reservoir 24 may be included in the fluid circuit 16. As such, the reservoir 24 may be in fluid communication with the aforementioned at least one passage 12 associated with the at least one aircraft component 14. The reservoir 24 may be sized to be able to store all the conditioning fluid 20 with (some) excess expansion volume. The reservoir 24 may be located further from the at least one aircraft component 14 than the at least one passage 12 provided in the at least one aircraft component 14. The reservoir 24 may for example be located near to an external 28V power input of the aircraft 100. Moreover, the reservoir 24 may be segregated from a high voltage (HV) system of the aircraft 100.

[0048] The thermal management system 10 may further comprise at least one valve 28a-b associated with the reservoir 24. The at least one valve 28a-b may for example comprise a first valve 28a at an inlet of the reservoir 24 and a second valve 28b at an outlet of the reservoir 24.

[0049] The thermal management system 10 may further comprise a heating and / or cooling element 30 associated with the reservoir 24. The heating and / or cooling element 30 may be arranged to heat and / or cool conditioning fluid 20 in the reservoir 24. The heating and / or cooling element 30 may for example be mounted to the reservoir 24. For heating, element 30 may for example comprise heat pump or a resistance heating element. For cooling, element 30 may for example comprise a vapor cycle machine. The heating and / or cooling element 30 may be powered by a power source 32 external of the aircraft 100. The (electric) power source 32 may for example be a 28V ground power unit (GPU), which may be connected via the above-mentioned external 28V power input. The power source 32 could also power the at least one pump 18. The thermal management system 10 may further comprise at least one control unit 34. The at least one control unit 34 may comprise hardware (such as at least one processor) and software. The at least one control unit 34 may be configured to control (one or more of) the at least one pump 18, the at least one valve 28a-b, and the heating and / or cooling element 30, as will be discussed in more detail hereinbelow.

[0050] The thermal management system 10 in fig. 2 may be on board the aircraft 100, as indicated by dotted rectangle in fig. 2.

[0051] In “normal” operation of the thermal management system 10 when the at least one aircraft component 14 requires conditioning, for example when the aircraft 100 is flying and the at least one aircraft component 14 being at least one propulsion battery unit powers at least one electric motor used in propulsion of the aircraft 100, the conditioning fluid 20 may be cooled by the heat exchanger 22, which cooled conditioning fluid 20 may be circulated by the at least one pump 18 through the at least one aircraft component 14 inside the at least one passage 12 for cooling the at least one aircraft component 14. When the at least one aircraft component 14 no longer requires conditioning (cooling), for example when the aircraft 100 has landed or when the at least one electric motor is turned off in flight, the at least one pump 18 may be turned off and the conditioning fluid 20 may be present throughout the fluid circuit 16.

[0052] Turning now to the method of fig. 1. The method may for example be performed when the aircraft 100 is parked on the ground G.

[0053] At (step) S1 , the method comprises obtaining an indication 36 that conditioning fluid 20 present in the at least one passage 12 associated with the at least one aircraft component 14 has reached or may reach a temperature outside the predetermined operating temperature range of the conditioning fluid 20 at a time when the at least one aircraft component 14 does not require conditioning by the conditioning fluid 20, for example when the aircraft 100 is parked on the ground G (as illustrated in figures 4a and 4b).

[0054] The indication 36 may for example be based one or more of: (a) input from at least one temperature sensor of the thermal management system 10, in particular for determining or estimating the temperature of the conditioning fluid 20; (b) a temperature forecast for the location of the aircraft 100 at the time when the at least one aircraft component 14 does not require conditioning; (c) a scheduled time of departure for the aircraft’s next flight; and (d) a time when the at least one aircraft component 14 requires conditioning. For example, input from the at least one temperature sensor may indicate that the current temperature of the conditioning fluid 20 is below Ti (but above the freezing point of the conditioning fluid 20) and the time to departure is longer (say 7h) than a typical turnaround time for the aircraft 100, whereby the conditioning fluid 20 present in the at least one passage 12 indeed has reached a temperature outside (below) the predetermined operating temperature range at a time when the at least one aircraft component 14 does not require conditioning. In another example, a temperature forecast for the location where the aircraft 100 is parked may indicate that the ambient temperature before the time of departure will be below Ti , whereby the conditioning fluid 20 present in the at least one passage 12 indeed may reach a temperature outside (below) the predetermined operating temperature range at a time when the at least one aircraft component 14 does not require conditioning. In yet another example, a temperature forecast for the location where the aircraft 100 is parked may indicate that the ambient temperature will be below Ti before the time when the at least one propulsion battery unit (aircraft component 14) is to be charged and hence requires conditioning.

[0055] The indication 36 may be obtained by the at least one control unit 34. Obtaining the indication 36 could include receiving the indication 36 (to the at least one control unit 34) from another entity or a human operator. Alternatively, obtaining the indication 36 may include the at least one control unit 34 determining that conditioning fluid 20 present in the at least one passage 12 has reached or may reach a temperature outside the predetermined operating temperature range of the conditioning fluid 20 at a time when the at least one aircraft component 14 does not require conditioning, e.g. based one or more of (a)-(d) as discussed above. Accordingly, one or more of (a)-(d) may here be input to the at least one control unit 34.

[0056] The method further comprises removing (step S2), in response to obtaining the indication 36, at least some of the conditioning fluid 20 from the at least one passage 12 to the reservoir 24, thereby at least partly emptying said at least one passage 12 of conditioning fluid 20. This step S2 may for example be performed when the indication 36 is obtained. Preferably a majority (>50%) of the conditioning fluid 20 present in the at least one passage 12 is removed to the reservoir 24, and more preferably (substantially) all of the conditioning fluid 20 present in the at least one passage 12 is removed to the reservoir 24.

[0057] In case the indication 36 is that the conditioning fluid 20 present in at least one passage 12 may reach a temperature outside the predetermined operating temperature range at a time when the at least one aircraft component 14 does not require conditioning, the conditioning fluid 20 may be removed from the at least one passage 12 to the reservoir 24 before the conditioning fluid 20 reaches a temperature outside the predetermined operating temperature range. Specifically, in case the indication 36 is that the conditioning fluid 20 present in at least one passage 12 (has reached or) may reach a temperature below the predetermined operating temperature range at a time when the at least one aircraft component 14 does not require conditioning, the conditioning fluid 20 should be removed from the at least one passage 12 to the reservoir 24 before the conditioning fluid freezes 20, e.g. before the temperature in the above-mentioned temperature forecast falls below the freezing point of the conditioning fluid 20.

[0058] The conditioning fluid 20 may be removed from the at least one passage 12 to the reservoir 24 by at least one pump, such as the at least one pump 18. The at least one pump 18 may for example be controlled by the at least one control unit 34. The at least one pump 18 may for example be turned on (e.g. by the at least one control unit 34) when the indication 36 is obtained. Moreover, the at least one pump 18 may be turned off (e.g. by the at least one control unit 34) when it is determined, by at least one of a conditioning fluid flow meter 38 and visual inspection, that at least a predetermined sufficient amount of the conditioning fluid 20 is removed from the at least one passage 12. The conditioning fluid flow meter 38 may be included in the fluid circuit 16, preferably between the at least one pump 18 and the at least one passage 12. Moreover, the conditioning fluid 20 removed to the reservoir 24 may be trapped in the reservoir 24 by closing the first and second valves 28a-b, e.g. as controlled by the at least one control unit 36.

[0059] The method further comprises causing (step S3) the temperature of the (removed) conditioning fluid 20 in the reservoir 24 to be within the predetermined operating temperature range. Causing the temperature of the conditioning fluid 20 in the reservoir 24 to be within the predetermined operating temperature range may include heating or cooling the conditioning fluid 20 in the reservoir 24 so that the temperature of the conditioning fluid 20 in the reservoir 24 reaches the predetermined operating temperature range. Causing the temperature of the conditioning fluid 20 in the reservoir 24 to be within the predetermined operating temperature range may for example include melting any conditioning fluid 20 that has frozen in the reservoir 24. Moreover, causing the temperature of the conditioning fluid 20 in the reservoir 24 to be within the predetermined operating temperature range could include maintaining the temperature of the conditioning fluid 20 in the reservoir 24 within the predetermined operating temperature range throughout the time the conditioning fluid 20 is in the reservoir 24 between steps S2 and S4.

[0060] The temperature of the conditioning fluid 20 in the reservoir 24 may be caused to be within said predetermined operating temperature range by the heating and / or cooling element 30 associated with the reservoir 24. The heating and / or cooling element 30 may for example be controlled by the at least one control unit 34. The heating and / or cooling element 30 may be powered by the external power source 32, which power source 32 may be temporarily connected to the heating and / or cooling element 30 in step S3.

[0061] The method further comprises returning (step S4) conditioning fluid 20 having its temperature within the predetermined operating temperature range from the reservoir 24 to the at least one passage 12, preferably in time to meet a requirement to condition said at least one aircraft component 14. It should be noted that it does not have to be the actual conditioning fluid 20 that was removed in step S2 that is returned in step S4, as the fluid circuit typically includes more conditioning fluid 20 than just the conditioning fluid 20 present in the passage(s) 12.

[0062] When to return the conditioning fluid 20 in the reservoir 20 to the at least one passage 12 in time to meet a requirement to condition the at least one aircraft component 14 may be based on a scheduled time of departure for the aircraft’s next flight and / or an ambient temperature of the aircraft 100. The conditioning fluid 20 may for example be returned at a predetermined time (e.g. 20 min) before the scheduled time of departure. In another example, the current ambient temperature has moved (well) withing the predetermined operating temperature range of the conditioning fluid 20, whereby conditioning fluid 20 may be returned from the from the reservoir 24 to the at least one passage 12 (though it may be kept in the reservoir 24 until just before departure). The conditioning fluid 20 may be returned from the reservoir 24 to the at least one passage 12 by at least one pump, such as the at least one pump 18. The at least one pump 18 may for example be controlled by the at least one control unit 34. Moreover, the conditioning fluid 20 to be returned may be released from the reservoir 24 by opening the first and second valves 28a-b closed in conjunction with step S2, e.g. as controlled by the at least one control unit 36.

[0063] After step S4, the above-mentioned “normal” operation of the thermal management system 10 may be resumed, e.g. when the aircraft 100 is flying (again).

[0064] Moreover, absent obtaining the indication 36, the conditioning fluid 20 may be kept in the at least one passage 12 even at the time when the at least one aircraft component 14 does not require conditioning.

[0065] Turning to fig. 3, in another embodiment of the thermal management system 10, the reservoir 24’ may be external of the aircraft 100. Also, the heating and / or cooling element 30 associated with the reservoir 24’ may be external of the aircraft 100. Alternatively, the heating and / or cooling element 30 associated with the reservoir 24’ could here be omitted, for example if the external reservoir 24’ is placed in a temperate environment, such as indoors.

[0066] The external reservoir 24’ may be temporarily connected to a fitting 40 of the aircraft 100, which fitting 40 is in fluid communication with a flow selector valve 42 on the fluid circuit 16, whereby the external reservoir 24’ may be temporarily in fluid communication with the at least one passage 12.

[0067] It should be noted that in the embodiment of fig. 3, the thermal management system 10 may comprise another reservoir 43 on board the aircraft 100. Reservoir 43 may be included in the fluid circuit 16 and be used in the “normal” operation of the thermal management system 10. Reservoir 43 may beneficially not need an expansion space to cover for volume expansion of conditioning fluid 20 due to high temperature.

[0068] The thermal management system 10 may here further comprise a pump 44 external of the aircraft 100. The external pump 44 may be arranged to remove at least some of the conditioning fluid 20 from the at least one passage 12 to the external reservoir (step S2), and to return conditioning fluid 20 from the external reservoir 24’ to the at least one passage 12 (step S4). Specifically, the pump 44 may be configured to remove all conditioning fluid 20 from the aircraft 100, and to return all that conditioning fluid 20 to the aircraft 100 at a later stage. The conditioning fluid 20 removed to the external reservoir 24’ may trapped in the external reservoir 24 by closing valve 28 associated with the external reservoir 24’, and the conditioning fluid 20 may be released from the external reservoir 24’ by opening the valve 28. The valve 28 may be provided at an inlet / outlet of the reservoir 24’.

[0069] The thermal management system 10 may here further comprise a control unit 46 external of the aircraft 100. The external control unit 46 may comprise hardware (such as at least one processor) and software. The external control unit 46 may be configured to obtain the indication 36, and to control (one or more of) the external pump 44, the valve 28, and the external heating and / or cooling element 30, to perform the aforementioned steps S1-S4.

[0070] The external control unit 46 may be in communication with the at least one (onboard) control unit 34, as indicated by the dash dot dot line in fig. 3. The communication may be wired or wireless. The external control unit 46 may for example instruct the at least one (onboard) control unit 34 to control the flow selector valve 42 in conjunction with performing steps S2 and S4. Moreover, the at least one (onboard) control unit 34 could communicate for example the above-mentioned input (a) to the external control unit 46.

[0071] The external reservoir 24’, the external pump 44, the valve 28, the external heating and / or cooling element 30, and the external control unit 46 may be included in a ground support equipment 48, as indicated by the dash dot rectangle in fig. 3.

[0072] Turning to figs. 4a-b, the thermal management system 10 may at least partly be installed in aircraft 100. The aircraft 100 may further comprise the at least one aircraft component 14.

[0073] As mentioned above, the at least one aircraft component 14 may for example be a plurality of propulsion battery units. The propulsion battery units may be for example be located under fuselage 102 or in the fuselage 102 of the aircraft 100. The propulsion battery units may be arranged to power one or more electric motors 104 of the aircraft 100. Each electric motor 104 may be coupled to a propeller 106.

[0074] The aircraft 100 may for example comprise four electrical motors 104 and propellers

[0075] 106, as in fig. 4a. The electrical motors 104 may be mounted (in nacelles) on wings 108 of the aircraft 100. The aircraft 100 may be configured for fully electric propulsion. The aircraft 100 could alternatively comprise an auxiliary power supply 110 for range extension / serial hybrid. The auxiliary power supply 110 may comprise a turbogenerator that runs on fuel, preferably sustainable aviation fuel (SAF). The auxiliary power supply 110 may be configured to power the electric motors 104 and / or to charge the propulsion battery units 14.

[0076] Also in fig. 4a, the (complete) thermal management system 10 including the reservoir 24 may be on board the aircraft 100.

[0077] In another embodiment of the aircraft, the propulsion battery units may be arranged to power one or more electric motors each paired with a turbine engine via e.g. a gearbox for driving a common propeller (i.e. parallel hybrid).

[0078] In yet another embodiment illustrated in fig. 4b, the aircraft 100 may comprise one or more propulsion battery units 14 arranged to power one or more electric motors 104 each coupled to a propeller 106, wherein the aircraft 100 further comprises one or more turboprop engines 112 being separate from one or more electric motors 104 and each coupled to its own propeller 114. The turboprop engines 112 may be powered by aviation fuel, preferably sustainable aviation fuel (SAF). The aircraft 100 may for example comprise two electric motors 104 and propellers 106, and two turboprop engines 112 and propellers 114. The electrical motors 104 and the turboprop engines 112 may be mounted (in nacelles) on the wings 108. The electrical motors 104 may for example be inboard of the turboprop engines 112, as in fig. 4b.

[0079] Fig. 4b also schematically illustrates the ground support equipment 48 from fig. 3, though it would be equally applicable to fig. 4a, and vice versa. The ground support equipment 48 may have wheels 50, to move it to / from the aircraft 100.

[0080] The aircraft 100 in figs. 4a-b may further comprise an empennage 116, a cockpit 118, a passenger cabin 120, flight control surfaces (such as ailerons, elevators, a rudder, flaps, air brakes, etc.), and landing gear 122. The aircraft 100 may for example be an airplane of fixed wing type with electric or hybrid electric propulsion and designed for conventional take-off and landing.

[0081] It should be appreciated that a flowchart comprises some operations which are illustrated with a solid border and some operations which are illustrated with a dashed border. The operations which are comprised in a solid border are operations which are comprised in the broadest example embodiment. The operations which are comprised in a dashed border are example embodiments which may be comprised in, or a part of, or are further operations which may be taken in addition to the operations of the broadest example embodiments. It should be appreciated that these operations need not be performed in order. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any order and in any combination.

[0082] Aspects of the disclosure are described with reference to the drawings, e.g., block diagrams and / or flowcharts. It is understood that several entities in the drawings, e.g., blocks of the block diagrams, and also combinations of entities in the drawings, can be implemented by computer program instructions, which instructions can be stored in a computer-readable memory, and also loaded onto a computer or other programmable data processing apparatus. Such computer program instructions can be provided to a processor of a general purpose computer, a special purpose computer and / or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer and / or other programmable data processing apparatus, create means for implementing the functions / acts specified in the block diagrams and / or flowchart block or blocks.

[0083] In some implementations and according to some aspects of the disclosure, the functions or steps noted in the blocks can occur out of the order noted in the operational illustrations. For example, two blocks shown in succession can in fact be executed substantially concurrently or the blocks can sometimes be executed in the reverse order, depending upon the functionality / acts involved. Also, the functions or steps noted in the blocks can according to some aspects of the disclosure be executed continuously in a loop.

[0084] In the drawings and specification, there have been disclosed exemplary aspects of the disclosure. However, many variations and modifications can be made to these aspects without substantially departing from the principles of the present disclosure. Thus, the disclosure should be regarded as illustrative rather than restrictive, and not as being limited to the particular aspects discussed above. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0085] The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other.

[0086] It should be noted that the word “comprising” does not necessarily exclude the presence of other elements or steps than those listed and the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several “means”, “units” or “devices” may be represented by the same item of hardware.

[0087] The various example embodiments described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

[0088] In the drawings and specification, there have been disclosed exemplary embodiments. However, many variations and modifications can be made to these embodiments. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the embodiments being defined by the following claims.

Claims

CLAIMS1 . A method of managing conditioning fluid of a thermal management system (10) for an aircraft (100), wherein the method comprises: obtaining an indication (36) that a conditioning fluid (20), which conditioning fluid is present in at least one passage (12) of the thermal management system for conditioning at least one aircraft component (14) associated with said at least one passage, has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning; removing, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to a reservoir (24; 24’) at least temporarily in fluid communication with said at least one passage, thereby at least partly emptying said at least one passage of conditioning fluid; causing the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and returning conditioning fluid (20) having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage.

2. The method according to claim 1 , wherein absent obtaining said indication the conditioning fluid is kept in the at least one passage at the time when the at least one aircraft component does not require conditioning.

3. The method according to claim 1 or 2, wherein the at least one aircraft component is located on board the aircraft, and wherein the aircraft is parked on ground (G) at the time when the at least one aircraft component does not require conditioning.

4. The method according to any one of the preceding claims, wherein the at least some conditioning fluid is removed from said at least one passage to the reservoir in response to obtaining said indication and before the conditioning fluid freezes.

5. The method according to any one of the preceding claims, wherein causing the temperature of the conditioning fluid in said reservoir to be within said predeterminedoperating temperature range includes melting the conditioning fluid that has frozen in the reservoir.

6. The method according to any one of the preceding claims, wherein conditioning fluid (20) having its temperature within said predetermined operating temperature range is returned from the reservoir to said at least one passage in time to meet a requirement to condition said at least one aircraft component.

7. The method according to any one of the preceding claims, wherein said indication is based on at least one of: input from at least one temperature sensor of the thermal management system; a temperature forecast for the location of the aircraft at the time when the at least one aircraft component does not require conditioning; a time of departure for the aircraft’s next flight; and a time when the at least one aircraft component requires conditioning.

8. The method according to any one of the preceding claims, wherein when to return the conditioning fluid in the reservoir to said at least one passage is based on at least one of: a time of departure for the aircraft’s next flight, and an ambient temperature of the aircraft.

9. The method according to any one of the preceding claims, wherein said reservoir is on board the aircraft.

10. The method according to any one of the preceding claims, wherein the conditioning fluid is removed from the at least one passage to the reservoir and returned from the reservoir to the at least one passage by at least one pump (18; 44).11 . The method according to any one of the preceding claims, wherein the conditioning fluid removed to the reservoir is trapped in the reservoir by closing at least one valve (28; 28a-b) associated with the reservoir, and wherein the conditioning fluid when about to return from the reservoir is released from the reservoir by opening at least one valve (28; 28a-b) associated with the reservoir.

12. The method according to any one of the preceding claims, wherein the method further comprises determining, by at least one of a conditioning fluid flow meter (38) and visual inspection, that at least a predetermined sufficient amount of the conditioning fluid is removed from the at least one passage.

13. The method according to any one of the preceding claims, wherein the temperature of the conditioning fluid in said reservoir is caused to be within said predetermined operating temperature range by a heating and / or cooling element (30) associated with said reservoir.

14. The method according to claim 10 and / or claim 13, wherein at least one of the at least one pump and the heating and / or cooling element is powered by a power source (32) external of the aircraft.

15. The method according to any one of the preceding claims, wherein said indication is obtained by at least one control unit (34; 46).

16. The method according to any one of the preceding claims, wherein said at least one aircraft component is at least one propulsion battery unit of said aircraft.

17. The method according to any one of the preceding claims, wherein said conditioning fluid is a liquid coolant.

18. A thermal management system (10) for an aircraft (100), the thermal management system comprising: at least one passage (12) for conditioning at least one aircraft component (14) associated with said at least one passage; a reservoir (24; 24’) at least temporarily in fluid communication with said at least one passage; and at least one control unit (34; 46) configured to:- obtain an indication that a conditioning fluid (20) present in the at least one passage has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning;- control at least one pump (18; 44) to remove, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to the reservoir, thereby at least partly emptying said at least one passage of conditioning fluid;- control a heating and / or cooling element (30) associated with said reservoir to cause the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and- control at least one pump (18; 44) to return conditioning fluid (20) having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage.

19. An aircraft (100), comprising: a thermal management system (10) according to claim 18; and the at least one aircraft component (14).

20. A computer program product comprising computer program code to perform, when executed on a computer (34; 46), the steps of: obtaining an indication that a conditioning fluid (20) present in at least one passage (12) for conditioning at least one aircraft component (14) associated with said at least one passage has reached or may reach a temperature outside a predetermined operating temperature range of said conditioning fluid at a time when the at least one aircraft component does not require conditioning; controlling at least one pump (18; 44) to remove, in response to obtaining said indication, at least some of the conditioning fluid from said at least one passage to a reservoir (24; 24’) at least temporarily in fluid communication with said at least one passage, thereby at least partly emptying said at least one passage of conditioning fluid; controlling a heating and / or cooling element (30) associated with said reservoir to cause the temperature of the conditioning fluid in said reservoir to be within said predetermined operating temperature range; and controlling at least one pump (18; 44) to return the conditioning fluid having its temperature within said predetermined operating temperature range from the reservoir to said at least one passage.

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